1. Field of the Invention
This invention relates to an overcurrent trip switch operable with a flux shunt trip device in a circuit breaker. More particularly, during a trip event the switch is actuated by an actuating member which interacts with the flux shunt trip device.
2. Background Information and Description of the Prior Art
Circuit breakers provide protection against various faults in an electrical power system such as overcurrent, ground faults and short circuits. It is desirable to provide an alarm assembly in a circuit breaker to generate an audible or a visual signal that the circuit breaker has tripped. This will allow an operator to receive an immediate indication that the system should be inspected and the cause of the trip investigated.
It has been known to provide alarm assemblies on certain circuit breakers in order to give either audible or visual indications that the circuit breaker has tripped. Typically, these alarms have been electronically controlled. More particularly, switches are activated by an associated power relay module which is purely electronic. The trip unit will send a signal to the power relay module which will set switches which may control an audible alarm or a light indicator. As mentioned above, this indicates to an operator that the circuit breaker has tripped.
The difficulty with such electronic devices is that they require control power. If power is lost in the system, the switches will not be activated under appropriate circumstances. Thus, there remains a need for a mechanically activated switching device which will operate without the need for separate control power. Some mechanically activated switches have been known to be provided on some circuit breakers, however, it has not heretofore been known to provide such a device which is operable in response to a flux shunt trip mechanism.
Some circuit breakers include a flux shunt trip mechanism. The flux shunt trip mechanism incorporates a permanent magnet. The device has a spring-loaded plunger which when released to an extended position causes the circuit breaker to trip. Under normal operating conditions, the plunger is maintained in a retracted position by the magnetic force of the permanent magnet. A trip coil is placed adjacent to the plunger. When the trip coil is energized upon a predetermined trip condition being reached, a magnetic flux is thereby generated. This magnetic flux opposes the magnetic flux of the permanent magnet. The opposing flux counterbalances the magnetic flux of the permanent magnet, and the spring force on the plunger then causes the plunger to move to its trip position.
There remains a further need for a mechanical device which can only be reset manually after it has been actuated by a trip event in the circuit breaker. There remains yet a further need for a mechanical device which interacts with the flux shunt trip mechanism of a circuit breaker.